1. Field of the Invention
The present invention relates to a substrate crack inspecting (examining, testing) method, a substrate crack inspection apparatus, and a solar battery module manufacturing method, and in detail, it relates to a method for inspecting a substrate for a crack by analyzing a sound produced by providing vibration for a substrate, an apparatus suitable for the method, and a solar battery module manufacturing method by use of solar cells selected by the method.
2. Description of Related Art
A solar battery is generally manufactured by the following method. First, a solar battery cell is manufactured by forming a pn junction and a pair of electrodes on a silicon wafer obtained by slicing a silicon ingot. Next, by electrically connecting a plurality of solar battery cells by use of an interconnector, arrayed solar battery cells (array cells) are obtained. Next, tempered glass, a sealing resin, array cells, a sealing resin, and a back film are laminated in this order. Then, after connecting the adjacent arrayed cells to each other and attaching a power outlet terminal line, sealing processing is carried out. After the sealing processing is completed, by attaching a terminal box to the power drawout terminal line and attaching a frame, a solar battery module is completed. The completed solar battery module is factory-shipped after an inspection of output characteristics is carried out by use of a solar simulator.
Inside the silicon wafer which is a cell material for a solar battery cell, a minute crack called a microcrack, namely, internal alligatoring may occur during its production. The solar battery cells with internal alligatoring sometimes fracture in the steps for manufacturing a solar battery module. If a solar battery cell fractures, it is necessary to carry out a restoring step to remove the fractured cell and mount another solar battery cell. As a result of an addition of a new operation as such, productivity of the solar battery modules declines. In addition, even when the aforementioned solar battery cells with microcracks are mounted without fracturing and completed as a solar battery module, the solar battery cells with microcracks are insufficient in power generating performance, therefore, in the completed solar battery module, a problem such as a decline in the power output as a whole occurs.
As a conventional method for detecting a microcrack, known is a method of previously applying to a substrate a stress substantially the same as a stress that the substrate receives at the time of a predetermined processing, adding another shock to the substrate, and detecting whether or not damage exists based on a produced sound (see Japanese Unexamined Patent Publication No. 2002-343989, for example.)
However, according to the conventional method, since an apparatus for applying a stress to the substrate is necessary, the manufacturing equipment is complicated, and a problem exists such that production efficiency declines.